Isaiah M. Castaneda Week 2

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Four Wild Plants: Green-1, Green-2, Red, White Objective: Discover how to produce a true breeding purple flower

First, it is valuable to explore each allele, the color each is responsible for, and the amino acid sequence of each. This way it will be easy to explore whether or not the answer to creating a true breeding purple flower can be found from an amino acid sequence standpoint.

(a) Allele Color amino acid sequence

Cg Green Met Ser Asn Arg His Ile Leu Leu Val Tyr Trp Arg Gln

Cb Blue Met Ser Asn Arg His Ile Leu Leu Val Tyr Cys Arg Gln

Cy Yellow Met Ser Asn Arg His Ile Leu Leu Val Trp Cys Arg Gln

Cr Red Met Ser Asn Arg His Ile Leu Leu Val Phe Cys Arg Gln

Cw White Met Ser Asn Arg His Ile Leu Leu Val Val Cys Arg Gln


(b) What features of a protein make it colored?

notes: 10th amino acid of non-colored flower is Val

I took a green-2 flower, which has blue and yellow alleles to make green. I replaced the 10th amino acid in the green allele with Val to create a white flower. I then replaced with the 10th AA of a true breeding white flower with His to see if this resulted in pigmentation. It did not. Replacing the 10h AA with Leu and Arg did not result in a colored flower either. However, Phe, Trp and Tyr in the 10th AA position all resulted in colored flowers. Replacing the 11th AA in the green allele with Arg or Tyr resulted in a white flower. Replacing it with Val or Leu created a blue color. Next, I experimented changing each position in the green allele. It was possible to create a white flower through a change in each position.

A colored protein contains Tyr, Trp, or Phe in the 10th position. They contain non-polar side chains and are aromatic. Pigments tend to have alternating double and single bonds. The aromatic amino acids Tyr, Trp, and Phe are important in producing colors.

(c) What features of the amino acid sequence make a protein a particular color?

The amount, presence, and combinations of Tyr, Trp, or Phe in or after the 10th AA position influences what color a protein is.

(d) How do the colors combine to produce an overall color? How does this explain the genotype-phenotype rules you found in part (I)?

White + any other than white = other color

White + white = white

Green + green, white, blue, or yellow = green

Green + red = black

Blue + white or blue= blue

Blue + green or yellow = Green

Blue + red = purple

Red + red or white = red

Red + blue = purple

Red + yellow = Orange

Red + green = black

Yellow + green or blue = green

Yellow + red = orange

Yellow + white or yellow = yellow

There are 5 primary colors in this species: green, blue, yellow, red, & white. White is recessive to all and therefore can only produce a white flower when crossed with another white. Green is codominant with red, creating a black pigment and dominant to white, blue, and yellow, creating green colored offspring. Blue is dominant to white, resulting in blue flowers when crossed, and codominant with red, which produces a purple color. Red is dominant to white and codominant with green, blue, and yellow (orange pigment). Yellow is dominant to white, recessive to green and blue, and codominant with red.


(e) Which proteins are found in each of the four starting organisms?

Green-1: Green & Green

Green-2: Blue & Yellow

Red: Red & White

White: White & White

(f) Sequence for a purple protein.

Met Ser Asn Arg His Ile Leu Leu Val Tyr Phe Cys Arg Gln

Upon combining various alleles, it was found that blue combined with red resulted in a purple color. The AA sequence for blue was Met Ser Asn Arg His Ile Leu Leu Val Tyr Cys Arg Gln The AA sequence for red was Met Ser Asn Arg His Ile Leu Leu Val Phe Cys Arg Gln Other crosses showed that the blue gene was recessive to the green gene, but was dominant to white. Also, Red was dominant to white and codominant with the other colors. The resulting purple color from crossing a red flower with a blue is indicative of co-dominance. The only difference between the red and blue sequences is the AA in the 10th position. For blue it is Tyr and for red it is Phe. Taking into consideration the previous statement made about co-dominance, I figured both amino acids needed to be present in order to create a true breeding purple flower. The results showed that this notion may be true. Further inspection showed a Tyr-Phe sequence starting with or after the 10th AA could be used to create a purple protein pretty much every time. However, if there was a Trp in this section, another Phe would be needed to create purple again. The reasoning behind this may be that Trp has a larger conjugated system, adding to the darkness of the color. It’s presence beside Tyr-Phe could therefore cause too deep of a pigment.


The main findings in this biochemical experiment were the following:

  1. It is, indeed, possible to create a true-breeding purple flower by altering the amino acid sequence.
  2. The 10th position and onward were critical in flower pigmentation.
  3. Altering positions before the 10th could result in a white flower.
  4. Tyr, Phe, and Trp are responsible for pigmentation due to their aromatic structures.
  5. There are multiple ways to create a purple protein, but the appropriate amino acid combination is necessary.

Some very exotic/insightful photos had been collected during the experiment, but due to Mac-Windows incompatibility these pictures could not be retrieved by my home station.

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